1. Field of the Invention
The present invention relates to an antenna having a small size, light weight, and high gain, being improved to have a wide tuning frequency band, and being suitable for mounting on a personal computer for example, to constitute a wireless LAN, i.e., Local Area Network.
2. Description of the Conventional Art
As a technology relating to the antenna having the small size and light weight, which is used for a terminal station of the wireless LAN or a portable type electronic equipment, “Non-direction antenna system and Notebook personal computer” described in Japanese Patent Laid Open No. 2001-345619 has been publicly known.
In FIG. 1, three kinds of the publicly known antenna being proposed for mounting on the personal computer are drawn in one figure. (In actual use, only one of the three antennas is installed.)
A code 17 shows a foldable antenna. This antenna can be used by setting up as shown with an arrow a, and can be housed as shown with an arrow b.
A code 18 shows a PC card having an antenna, and this PC card is inserted into a main body of a personal computer 14 as shown with an arrow c. As for this PC card, the edge is projected a little in the inserted state as shown with a solid line, and the antenna is prepared at this projection part.
A code 19 shows a rod antenna, and can be telescopically extended and contracted.
These three antennas shown in FIG. 1 have merits and demerits respectively, and are not perfect.
The fordable antenna 17 must be raised and lowered by a fingertip at the time of starting and ending of use, thus it is troublesome.
As for the PC card having the antenna 18 and the rod antenna 19, since an antenna element is projected from the main body of the personal computer 14, there is a problem for this element being caught if not taking care.
Further, the foldable antenna 17 and the PC card 18 having the antenna are influenced by the main body of the personal computer 14, thus there are problems that an antenna gain in 270 degree direction in the figure is inferior as compared with the antenna gain in 90 degree direction.
In addition, these three antennas are visible in appearance to damage a value in a design, thus the commodity value is decreased.
Furthermore, these publicly known antennas are tuned only at a specific frequency band, and have not a multi-frequency property (a dual band property). Thereby, for example, when the transmitting and receiving by the diversity system are carried out, it is necessary to prepare two sets of the antenna.
The present invention was carried out in order to solve the above problems, and has an object to provide a new technology of an antenna having the remarkably small size, the light weight and especially a ultra-thin, wherein an hand operation, such as extension and contraction, raising and lowering, or the like, is not necessity at the time of starting and ending of the use, and an antenna gain is high. Further, this antenna technology is suitable for an industrially mass-producing with a low production cost. In addition, in this antenna technology, the antenna is not projected from the instrument for mounting, thus the value in the design is not damaged.
If such the antenna device is developed, the antenna can be housed and set in a backside of a liquid crystal display or a plastic frame in the personal computer 14, for example, like an antenna 5 shown with a virtual line (chain line) in FIG. 1.